Runners are known to be a little obsessed with their sport – but for good reason. What’s not to love about an activity that brings endorphins, stress relief, fresh air, and makes you feel good about yourself?

With all of the confidence and health boosting support, it’s easy to become a little obsessed with running. We challenge ourselves to run a little further or a little faster more often than not. But before we know it, what started out as a quest for improvement can develop into something more dangerous: overtraining syndrome.

What is Overtraining Syndrome?

Basically, overtraining syndrome is exactly what it sounds like: over-training. It occurs when you are running too many miles and/or pushing your body too hard on each run.

Related: How Running Lower Mileage Will Make Running Feel Easier

The tricky part is that each runner has a different threshold for overtraining. Some ultramarathoners may be able to train easily at 100 miles a week, while many new runners struggle to surpass 15. That’s not to say that one runner is in better shape than another – it just means that everyone’s body is different.

Overtraining can happen in any sport, but with the obsessive, self-competitive nature of runners, it is commonly experienced in runners of all ability levels.

A runner is considered to be ‘overtraining’ when they are completing more mileage and activity on a regular basis than what their body can recover from, causing their performance to plateau or even decline.

Is Overtraining Dangerous?

It’s easy to brush overtraining off as something that isn’t very serious. Especially when compared to a specific injury, it might sound like no big deal.

However, overtraining can lead to a variety of circumstances that are a big deal. Overtraining is a common cause for both mental and physical burnout, performance decline, many different injuries, poor sleep and an elevated resting heart rate.

Related: 4 Signs of Running Burnout (and How to Recover)

You might be able to recover after pushing your body to its limits once and a while, but doing so on a regular basis creates continuous stress. This physical stress will not only inhibit your progress, but it could potentially take you out of the running game for a while.

How to Tell if You’re Overtraining

It can be difficult to hold yourself back from adding a few extra miles to your long run or fitting in another interval during your speed workout when you’re feeling great. If your body is feeling good, what’s the harm in doing just a little more – right?

Wrong.

Sure, sometimes we are perfectly capable of adding that extra mile. But when you’ve reached your current fitness limit, adding that extra mile might be the difference between continuing your training for that new PR or taking a month or more off to recover.

Runners usually don’t even realize that they are overtraining until it is too late. More often than not, it takes many negative experiences for runners to question their training.

Every runner is different, and it’s important avoid comparing yourself to someone else. Really listen to your body during and after each run to note how it is responding to the effort.

Here are a few signs of overtraining to look out for. If you are experiencing any of these overtraining symptoms, take a break or scale back your training load to allow your body to recover.

Signs of Overtraining

Elevated resting heart rate.

If you notice that your resting heart rate is higher than usual, it could be a sign of overtraining. This elevated heart rate might be an indicator that your body is still working harder and trying to recover from previous workouts, even when you are at rest.

Poor quality of sleep.

When you find yourself unable to fall asleep or sleeping poorly throughout the night, it’s time to reevaluate your training. Intense training loads may actually decrease your quality of sleep or make it difficult for you to fall asleep each night, even after hard workouts.

Decreased appetite.

If you used to gulp down your dinner and now are struggling to finish it, this may be an indicator of overtraining. Changes in appetite or weight are often a red flag – signaling that your body is in a constant state of stress from overtraining.

Frequent illness.

Catching a cold during the winter or from your coworker is one thing, but if you find yourself continuously feeling under the weather – overtraining might be to blame. When your body is pushed beyond its limits it winds up in a constant state of stress, leaving your immune system weak and defenseless against minor illness.

Normal workouts require harder efforts.

One of the biggest signs of overtraining is noticing that your usual workouts feel significantly harder than usual. If you run the same four mile loop each Tuesday and notice that you’re suddenly feeling out of breath and slow this week – you might be overtraining.

If you train with a heart rate monitor, you may notice that your heart rate is higher when you are running your usual pace. If running at your normal speed suddenly feels much more challenging, it might be time to take a step back.

Lingering soreness or pain.

Similar to being unable to fight off illness, your body recovers slower from injury and workout stress when you are overtraining. The harder efforts each week leave your body with less time to recover from more intense stress. Feeling sore for days after a normal run could be a sign that you are overtraining.

Declining running performance.

There’s nothing more frustrating than feeling like you’re putting in more effort and getting nothing in return. If you’re ramped up your effort on the run and find the mileage feeling too difficult or your pace slowing down, you might actually be training too much.

How to Prevent Overtraining

Lucky for us, preventing overtraining can be as simple as listening to your body. Stay tuned to your body with each run and recovery, and try not to compare yourself to others.

It’s so easy to hear of another runner’s accomplishments and assume that we should be doing more. Remember that one of the best parts about running is that this sport is about our individual accomplishments. Take the time to celebrate with others, but run your own race.

Keep track of your own progress and individual accomplishments to celebrate the wins along the way. Listen to your body each week. If you’re feeling really good, push it just a little. When you feel tired or stressed, go easy on yourself.

Give yourself plenty of time to recover after each run. Incorporate stretching, cross training, foam rolling and strength training in your training schedule. And most importantly: rest. Give yourself at least one rest day each week to recharge, refresh and rejuvenate your mind.

More overtraining tips and advice:

• 4 Signs of Running Burnout (and How to Recover)
• How to Overcome a Running Plateau
• 6 Ways to Break Out of a Fitness Rut
• 5 Reasons to Embrace Easy Running